Signal receiving system



May 28, 1940. w. LA v. CARLSON 2,202,141

' SIGNAL RECEIVING SYSTEM Filed Feb. 25, 1931 RECEIVER SOCKET-POWER UNIT INVENTOR.

ZlrendeZZ L. Carlson,

HAS ATTORNEY.

Patented May 28, 1940 UNITED s'rn'r SIGNAL RECEIVING SYSTEM Wendell La Verne Carlson, Haddonfield, N. 1.,

assignor, by mesne assignments, to Radio Corporation of America, New York, N.'Y., a corporation of Delaware Application February 25, 1931, Serial No. 518,113

Claims. (01. 25020 10, from electric motors, electric bells, electric irons,

sparking elevator control contacts, violet-ray machines and the like, is common in "urban districts and is particularly unpleasant in large apartment houses.

Numerous attempts have, heretofore, been made to improve radio reception by shielding but insofar as I am awareno one, previous to my invention, has provided a signal receiving system whereby substantially all undesired etheric disturbances of the aforementioned types are prevented frommarring the quality of the received signals. i

It is, accordingly, an object of my present invention to provide a radio receiving system in-' cluding an antenna that shall be substantially immune to the effects of etheric disturbances other than those affecting the antenna proper.

Another object of my invention is to provide a radio receiving system that may successfully ,be used in urban districts where etheric disturbance is maximum.

A still further object of my invention is to substantially eliminate the radiation of disturbances from a radio receiver of the type wherein oscillations are generated during the operation of signal reception. i

My study of reception interference in urban districts has indicated that the zones of disturbance, occasioned by sparking contacts and .the like, are rather limited and that if an energy receiving device, such as an antenna-ground system or an antenna and counterpoise, is remotely disposed, as upon the roof of an apartment house, the amount of local etheric disturbance picked up thereby is negligible.

I have, further, established the fact that a large amount of local disturbance is conveyed to a radio receiver by way of the conductors that supply plate and filament potentials to the thermionic tubes. The latter source of noise is particularly important in the event that the receiver is of the type including a socket power unit which converts commercial alternating current into direct current, at the proper potentials, for tube energizing, since substantially all as TENT OFFICE of the sources of disturbance are mediately or immediately connected to the alternating current receiver.

, distribution system which supplies the radio I have, also, established the fact that the interelement connections in the radio receiver,

such as radio-frequency coils and the like, when the said receiver is operated in a zone of proenough disturbing energy to seriously 'nounced etheric' disturbance, can easily pick up interfere stances, will receive sufficient disturbin to render reception substantially impossible no matter how carefully the receiver is shielded.

According to my invention, therefore,

g energy I dispose an energy receiving device, such as an antenna oounterpoise system, outside of the zone of pronounced etheric disturbance and I enclose the 7 radio receiving apparatus and the sock unit therefor within a receptacle which shielded.

I' provide improved means for conveying energy from the antenna-system to the ct power is totally receiver,

constituted by a shielded low impedance transmissionline, and I interpose a properly designed low-pass filter between the alternating current distribution system and the socket power unit. For best results I also find it advantageous to completely shield the line filter in order that the inductors included in it shall not, themselves, be capable of picking up disturbing energy.

The novel features that I-c'onsider characteristic of my invention are set forth with larity in the appended claims.

particu- The invention itself, however, both as to its organization and its method of operation, together with a dditional objects and. advantages thereof, will best be understood from the following description of a specific embodiment when read in connection with the accompanying drawing.

The single figure of the drawing-is a diagramone modification of my invention.

The apparatus illustrated in the dra matic view of a radio receiving system embodying wing includes a radio receiver l,,a loudspeaker 3 and a socket power unit 5 disposed within a grounded metallic inclosure I that is impervious to etheric disturbances. by a completely shielded chassis, by

The inclosure may be constituted shielding applied to a cabinet or the like, or it may'take the form of a room, the walls of which are made of metal screen. Signal receiving means, preferably co nstituted tioned remotely from theinclosure which houses the signal amplifying apparatus, the loading coil being mounted in a grounded metallic container iii.

A coupling coil ll, of a few turns, is disposed in inductive relation to the loading coil, the terminals of the coupling coil being connected to a transmission line l9 which provides the antenna down-lead or lead-in conductor and extends, through a grounded metallic conduit 2|, to a similar coil 23 mounted within the inclosure. The small coil within the inclosure may be coupled directly to the tuned input circuit 25 of the signal amplifying apparatus or a filter system, exemplified by an inductor 27 and a tuning condenser 29, may be interposed between it and the.

commercially as Radiola 80, wherein a filter circuit such as is illustrated is employed, I have chosen that receiver for purposes of explanation. My invention, however, is not' to be considered as being restricted thereto.

The socket power unit 5 is connected to a source 3! of commercial alternating current through a low-pass filter comprising a plurality of series inductors 33 and shunting condensers 35. Each stage of the filter is preferably shielded from the preceding and following stages and as many stages as are necessary may be employed. The entire filter is enclosed in a metallic container 31 which may be mounted within the mainv inclosure or may be disposed exteriorly thereof.

The opening through which sound is emitted from the loudspeaker is also provided with a shielding screen 39 and a similar opening M or a plurality of opening may be provided in the walls of the inclosure to provide ventilation and to prevent resonance effects therein if precaution is taken to thoroughly shield the additional openings.

In order that the signal amplifying apparatus may be controlled and tuned from a point exterior of the inclosure, it is preferable to utilize actuating devices having metallic shafts since the said shafts may extend through closely fitting bushings in the inclosure without destroying the electric continuity thereof. Such tuning devices are exemplified by a control knob 43 and shaft 45 shown in the drawing.

I have found it quite desirable to connect the leading shield to ground at a number of points and it is sometimes advisable to also connect the inclosure to ground at a plurality of points to prevent large eddy currents from circulating therein.

When it is inconvenient to provide a shielding inclosure as shown it may be desirable to provide a separate shield for the receiver and the input coils therefor, a separate shield for-the socket power unit, and additional shields for certain portions of the power supply 01' socket power unit and the line filterall otherwise exposed connecting wires, such as between the power supply or socket power unit and the receiver. The receiver and the loud speaker, in such event, may also be shielded for best results, or appropriate filters may be provided without departing from my invention.

In a preferred commercial embodiment of my invention, wherein the signal amplifying apparatus is of the type known as Radiola 80, the terminating coil 23 of the transmission line ,is constituted by four turns of #31 cotton and enamel covered wire Wound directly over or beside the low potential end of the link coil 2! in the filter circuit. In the Radiola the link coil included approximately 114 turns on a winding form approximately one and one-quarter inches in diameter. The transmission line is a two-conductor twisted pair, each conductor being constituted by 10 tinned cotton-wrapped copper wires having a diameter of .010", the twist of the conductors having a pitch of approximately one turn every two inches. The shielding over the transmission line is preferably braided copper .wire.

The loading coil IS in the antenna circuit has an inductance of about four millihenries and the coupling coil l'!, which connects to the transmission line, is preferably approximately 15 turns of #30 copper wire, both coils being wound on a form having a diameter of 1 The coupling between the coils is close.

It will be apparent from a consideration of the foregoing description of my improved signal receiving system that it is substantially immune to etheric disturbances other than those received by the antenna proper. Disturbances caused by sparking commutators, faulty contacts and the like, which have quite high decrement, are effectively prevented from entering the received by the line filter. The line filter also prevents unwanted radio signals from being impressed upon the tubes and coils in the receiver and adds materially to the selectivity of the system. The low impedance link circuit constituted by the transmission line and the terminating inductors is shielded against disturbance by the grounded conduit and functions only to convey energy from the antenna system alone to the receiver.

Furthermore, my improved system, by reason of the complete shielding and line-filtering, pre vents substantially all disturbances originating therein from efiecting the reception of signals by other nearby receivers. This latter feature I consider to be very important and its importance will, undoubtedly, increase in the future.

My improved system, therefore, may be utilized for radio reception in zones of severe etheric disturbance and is of great utility in urban districts and for installation in apartment houses.

Although I have illustrated and described a specific-embodiment of my invention, numerous modifications thereof will be apparent to those skilled in the art to which it pertains. My invention, therefore, is not to be limited except insofar as is necessitated by the prior art and by the spirit of the appended claims.

I claim as my invention:

1. A radio receiver having a noise suppressor comprising in combination, an antenna relatively remote from said receiver, an ungrounded transmission loop extending between said antenna and said receiver, said loop comprising a twisted pair of conductors, means for coupling said loop at one end with said antenna and at the other end with said radio receiver, said coupling means at the antenna providing a stepdown ratio lower than the step-up ratio of the coupling means at the receiver, and shielding means totally enclosing said antenna coupling means, transmission loop and the receiver and receiver coupling means, said shielding means being grounded adjacent to the antenna and adjacent to the receiver.

2. In a signal receiving system, the combination of a receiving apparatus including a radio receiver, a power supply unit therefor and a grounded metallic shield enclosing said receiver and unit, said shield being substantially impervious to etheric disturbances, whereby said apparatus is adapted to be located in a zone subject to such disturbances, a shielded filter in circuit with said power supply unit and located within the confines of the metallic shield and grounded thereto, signal energy receiving means adapted to be located remotely from said apparatus and said zone of disturbances, said means including an antenna system, a loading impedance device for said antenna system, a grounded metallic container surrounding said impedance device, a metallic shield conduit connected with said container and with said apparatus shield and being grounded at more than one point along its length including a point adjacent the antenna end, and means providing a low impedance ungrounded two-wire transmission line between said loading impedance device and said radio receiver.

3. In a signal receiving system, a grounded metallic shield means providing an electrical apparatus enclosure substantially impervious to etheric disturbances, radio receiver apparatus located in said enclosure, whereby said apparatus may be effectively operated in a zone of etheric disturbances, and means for supplying signal energy to said apparatus without conveying thereto electrical potentials resultingfrom said disturbances, said means including an ungrounded two-wire low impedance signal energy transmission line connected with the receiver and having a receiving terminal device adapted to be located outside said region of etheric disturbances, and a grounded metallic shield conduit enclosing said device and transmission line and connected with the metallic shield means, said conduit being grounded at a plurality of points along its length including a point adjacent to said device.

4. In a signal receiving system, the combination of a signal receiver having a signal input circuit, an electrical shield enclosure means surrounding said receiver input circuit, and means for conveying radio signals within said inclosure means comprising an antenna system remotely located from the receiver, a shielded impedancematching and loading device for the antenna located adjacent thereto, a two-wire ungrounded transmission line providing a signal path between said last named means and the receiver input circuit, an electrical shield for the transmission line connected at one end with the shield of said impedance-matching and loading device for the antenna and at its opposite end with the shielded receiver, whereby the shielding of said receiving system is completed, and means providing a plurality of ground connections along said shield between the antenna and said receiver at a plurality of points including points adjacent to said antenna impedance-matching and loading device and said receiver, and at an intermediate point therebetween.

5. The combination with a radio receiver and an antenna system therefor remotely located with respect to the receiver, of a two-wire low impedance transmission line extending between said antenna system and said receiver, means providing a step-down transformer coupling the antenna system with the transmission line, step up transformer means coupling the transmission line with the receiver at the opposite end of said transmission line, electrical shield means surrounding said transformer means, an electrical shield surrounding said transmission line and connected with the first named shield means, and means for grounding said shield and shield means adjacent to the antenna system and adjacent to the receiver. I

6. The combination with a radio receiver and an antenna system therefor remotely located with respect to the receiver, of a two-wire low impedance transmission line extending between said antenna system and said receiver, means providing a step down transformer coupling the antenna system with the transmission line, step up transformer means coupling the transmission line with the receiver at the opposite end of said transmission line, an electrical shield surrounding said transformer means, an electrical shield surrounding said transmission line and connected with the first named shield means, and means for grounding said transformer shield adjacent to the antenna system and the transmission line shield adjacent to the receiver, the step down turns ratio of the transformer means adjacent to the antenna system being somewhat less than the step up turns ratio of the transformer means at the receiver.

7. In a system for protecting a radio receiver from local interference, in combination, an antenna, an ungrounded two-wire transmission line extending from said antenna to said receiver, a conducting sheath surrounding said line over substantially its entire length, means providing ground connections for said sheath adjacent to the head and foot ends thereof, a step-down transformer interposed between said antenna and the head of said line and a step-up transformer interposed between the foot of said line and said receiver, the step-down turns ratio of said transformer being somewhat less than the stepup turns ratios of said second transformer.

8. In a system for protecting a radio receiver from local interference, in combination, an antenna, a lead-in from said antenna to said receiver, a grounded conducting sheath surrounding said lead-in over substantially its entire length, a step-down transformer interposed between said antenna and the head of said lead-in and a step-up transformer interposed between the foot of said lead-in and said receiver, the step-down turns ratio of said first transformer being somewhat less than the step-up turns ratio of said second transformer.

9. A radio receiver having a noise suppressor comprising, in combination, an antenna relatively remote from said receiver, an ungrounded transmission loop extending between said antenna and said receiver, said loop comprising a twisted pair of conductors, means for coupling said loop at one end with said antenna and at the other pedance transmission line extending between said antenna system and said receiver, means proshield surrounding said transmission line and connected with the first named shield means, and means for grounding said shield and shield means.

WENDELL LA VERNE CARLSON. 

